The variation of vegetation greenness and underlying mechanisms in Guangdong province of China during 2001-2013 based on MODIS data.

This study explored the spatiotemporal variation of vegetation greenness and the mechanisms underlying this variation in the subtropical region of Guangdong in China during 2001-2013 to obtain a better understanding of vegetation response to climate and land use/cover changes in warm-humid regions. Satellite-based vegetation indices, land use/cover data and observed weather records during 2001-2013 were used. Univariate and multivariate linear regressions were conducted to quantify the trends and variations in vegetation greenness and the relationships with climate and land use/cover changes. The results indicated that the annual mean greenness trended upward significantly in eastern and western Guangdong and downward significantly in northern Guangdong. The patterns of significant positive or negative relationships between vegetation greenness and climatic factors were observed at the sub-regional scale. In addition, our results showed that (i) vegetation greenness in Guangdong was more sensitive to changes in temperature than in precipitation, (ii) spring temperature had an important time-lag effect on seasonal mean greenness in the following summer and autumn, and (iii) winter greenness depended largely on vegetation growth in the previous autumn. Furthermore, the conversion of grasslands and croplands to evergreen forests resulting from afforestation increased the vegetation greenness in eastern and western Guangdong. Overall, our results suggest that afforestation plays a dominant role in increasing vegetation cover/greenness in Guangdong whereas the effects of land use/cover change on vegetation growth are subject to climatic conditions. Thus, a better understanding of terrestrial vegetation dynamics requires considering both climate and land use/cover changes.